.Why did you take a taxi____you could come here by bus?
The thought they could the whole continent was exciting.
_________ life will continue on the earth for millions of years to come will depend on __________ this problem can be solved.
--May I open the window to let in some fresh air?-- __________
__________ is even more important is _________ the earth cooled down, water began to appear on its surface.
If you ______ smoke, please go outside.